Method of processing lubricating oil



United States Patent 2,961,144 METHOD or rnocnssmc LUBRICA'IING on.

Edward L. Cole, Glenham, N.Y., signal to Texaco Inc., a corporation of Delaware No Drawing. Filed Jan. 24, 19 58, Ser. No. 710,875

Claims. (Cl. 208-87) tion, a parafin base residual lubricating oil is refined by subjecting said base oil to propane deasphalting, furfural refining and methyl ethyl ketone-benzene solvent Fl 'axing; thereafter the resulting deasphalted,- furfural -refined, solvent dewaxed oil is contacted with hydrogen under mild hydrogenation conditions of temperature and pressure in the presence of a hydrogenation catalyst for a period suflicient to effect reactions causing increased stability to thin film oxidation at high temperatures. y

it is known to refine lubricating oils by methods including the steps of distillation, solvent refining, acid treating, clay contacting and solvent dewaxing. When residual type lubricating oils are processed, an additional step of deasphalting is usually required. In the processing steps listed above, distillation is employed as a means of separating the crude oil into fractions of suitable molecular weight and viscosity. Solvent refining, with, for example, furfural, sulfur dioxide or phenol, is ordinarily used as a means of removing cyclic compounds and thereby improving the viscosity temperature properties of the treated oil. Acid treating is employed to improve the color, stability and resistance to oxidation of lubricating oils. Clay contacting is used to further improve the color and to remove residual traces of acids in the oil.

the presence of a hydrogenation catalyst is well known Solvent dewaxing is used to lower the pour point of the oil, and deasphalting is employed to remove .asphaltic bodies.

2,967,144 P t gedJan. 3, 1961 in the prior art. Wide ranges of temperature and pressure conditions have been employed in conducting this type of reaction, with the particular conditions selected depending on the degree of hydrogenation desired. The amount of hydrogenation effected increases with increasing temperatures and pressures. Under relatively mild reaction conditions color bodies in the charge oil can be reacted upon to achieve an improvement in color and color stability without substantially altering other physical properties of the ,oil. Under more severe hydrogenating conditions substantial desulfurization of the charge oil can be effected by conversion of contained sulfur compounds to hydrogen sulfide, and substantial alteration of the physical properties of the oil can be achieved through hydrogenation of aromatics or other unsaturated compounds present in the charge material.

Numerous hydrogenating catalysts have been proposed for carrying out such reactions. Examples are nickel, molybdenum, tungsten, vanadium, tin, zinc, chromium, iron and cobalt, and particularly the oxides and sulfides of these metals. Promoters comprising'oxides of other metals have been used in admixture, with such catalysts to increase their hydrogenating activity. Carriers such as alumina, silica gel, magnesium oxide and the like have also been employed. The present. process is an improvement over these known. refining processes. I have surprisingly found that under reaction conditions hereinafter specified and with certain mild hydrogenation catalysts, one can produce a residual oil fraction having improved stability to thinfilm, high temperature oxidation, so that it is outstanding as an aircraft engine oil.

In accordance with the process of the present inven tion a paraffin base residual lubricating oil base stock is first subjected to a refining sequence consisting essentially of a propane deasphalting step to remove the asphalticbodies, a furfural refining step to remove cyclic compounds, and a solvent dcwaxing step wherein the solvent comprises a mixture of methyl-ethyl-ketone and benzene to decrease the pour point of the solvent refined oil.

The deasphalted, furfural refined and dewaxed lubricating oil stock is then treated with added hydrogen in the presence of a mild hydrogenation catalyst under conditions of temperature, pressure and feed stock space velocity to effect reactions whereby the characteristics of the oil being hydrogenated are altered to produce an oil product of improved quality, i.e., increased stability to thin-film, high temperature oxidation.

Suitable mild hydrogenation catalysts that may be employed in the process of the invention are those formed from metals of the 6th and 8th groups of the periodic table,'their oxides or mixtures thereof. It is preferred to employ a molybdenum sulfide catalyst on an alumina carrier, the catalyst containing essentially about 20 percent molybdenum sulfide on alumina.

Cobalt molybdate catalysts comprising mixtures of cobalt oxide and molybdenum oxide have also been found to be satisfactory for use in the process of the invention. The cobalt molybdate catalysts known in the art generally contain from 5 percent to percent of the combined spam The operating temperature range for the hydrogenation step can vary from about 400 F. to about 650' F. without adversely afiecting the resultant product, but for maximum beneficial results it is preferred to maintain the operating temperature at a range of from about 500 F. to 600 F. with a-range of about 525 to 575 being especially preferred.

Pressures varying from about 200 p.s.i.g. to about 2000 p.s.i.g. can be employed in the hydrogenation step with a pressure range that varies from about 500 p.s.i.g. to about 1000 p.s.i.g. being an especially preferred operating range.

A space velocity of from about 0.1 to about 2.0 volumes of lubricating oil charged to the hydrogenation reactor per volume of catalyst per hour has been found to be satisfactory with a space velocity within the range of from about 0.25 to 0.50 volume of oil being preferred, for the most satisfactory results.

Although the net consumption of hydrogen gas is some- .what dependent on the conditions of temperature, pressure and space velocity employed in the hydrogenation step a representative value may vary from about 50 to 350 cubic feet of hydrogen per barrel of lubricating oil charged to the reactor. Recycle hydrogen feed rates including fresh hydrogen to make up for the hydrogen consumed in the reactor are also dependent on the selected operating conditions. Suitably, recycle feed rates may vary from about 1000 standard cubic feet per barrel (s.c.f./bbl.) of charge stock to as much as 10,000 s.c.f./bbl. with feed rates of about 2500 to 4200 s.c.f./hbl. being especially preferred.

The following examples are illustrative of the process of the present invention.

EXAMPLE 1 A lubricating oil fraction obtained from the residuum of a parafiin base West Texas crude was propane doasphalted, furfural refined and methyl ethyl ketone-benzene dewaxed to produce a lubricating oil charge stock. Inspection tests on the resulting lubricating oil charge stock are shown in column A of Table I below.

The lubricating oil charge stock then was further refined by contacting the oil with hydrogen at a temperature of about 500 F., a pressure of 500 p.s.i.g. in the presence of molybdenum sulfide catalyst employing a space velocity of 1.44. I

Inspection tests on the resultant hydrogen-treated oil are shown in column B of Table I below.

EXAMPLE 2 A paraflin base residual lubricating oil fraction obtained from a Lafitte crude was refined by subjecting the residual fraction to the steps of propane deasphalting, furfural refining and methyl ethyl ketone-benzcne dewaxing.

The resulting treated lubricating oil charge stock was then contacted by treatment with hydrogen under the following conditions: Temperature 607 F.; pressure 500 p.s.i.g.; catalyst molybdenum sulfide on alumina; space velocity 0.47; recycle hydrogen feed rate including fresh hydrogen to make up for the amount of hydrogen consumed 4100 s.c.f./bbl.

' Inspection tests on the charge stock and the hydrofinished product are set forth in columns C and D of Table I below.

EXAMPLE 3 A charge stock of a propane deasphalted, furfural refined methyl ethyl ketone-benzene dewaxed parafiin base residual fraction from a West Texas crude was hydrogenated in the presence of a molybdenum sulfide hydrogenation catalyst at a temperature of 417 F., 500 p.s.i.g. employing a space velocity of 0.50 and a hydrogen recycle rate of 3600 s.c.f./bbl. Inspection tests on the charge stock and hydrogenated product are presented in columns E and F of Table I.

EXAMPLE 4 The lubricating oil charge stock of Example 3 was hydrogenated in the presence of a molybdenum sulfide catalyst at a temperature of 465' F. a pressure of 500 p.s.i.g., a space velocity of 0.56, with a recycle hydrogen feed rate of 3200 s.c.f./bbl. Inspection tests on the charge stock and the product oil are likewise shown in Table I, columns 6 and H.

EXAMPLE 5 A heavy lubricating oil charge stock comprising 55 percent by volume of a propane deasphalted, furfural refined, and methyl ethyl ketone-benzene dewaxed paraffin base residuum having a viscosity of 118 SUS at 210' F., and 45 percent by volume of a propane deasphalted, furfural refined, and methyl ethyl ketone benzene dewaxed paraifin base residuum having a viscosity of 145.9 SUS at 210' F. was hydrogenated in the presence of cobalt molybdate catalyst comprising 3 percent cobalt oxide, 10 percent molybdenum oxide, 5 percent silica, 80 percent alumina, the balance carbon and incidental impurities, at a temperature of about 575 F., a pressure of 2000 p.s.i.g., and a space velocity of 0.25.

Inspection tests on the charge stock blend and the hydrofinished lubricating oil product are shown in Table I, columns I and I.

EXAMPLE 6 The blended charge stock of Example 5 was also treated with hydrogen in the presence of a hydrogenation catalyst comprising molybdenum sulfide on alumina at a temperature of about 575 F., a pressure of about 1000 p.s.i.g., and a space velocity of 0.23. Inspection tests on the hydrofinished product are shown in column L of Table I. For purposes of comparison, the data obtained from inspection tests on the charge stock blend are also shown in column K.

EXAMPLE 7 A paramn base residual lubricating oil fraction was propane deasphalted, furfural refined, methyl ethyl ketone-benzene dewaxed to form a charge stock which was thereafter treated with hydrogen in the presence of a molybdenum sulfide catalyst on alumina to produce a refined lubricating oil product.

The conditions employed in the hydrogenation step were 606' F., 500 p.s.i.g., space velocity of 1.70 and recycle hydrogen rate 3360 s.c.f./bbl.

Inspection tests on the charge stock and the refined oil product are presented in columns M and N of Table I.

EXAMPLE 8 The deasphalted, solvent refined, dewaxed charge stock of Example 2 was also treated with hydrogen in the presence of a molybdenum sulfide catalyst on alumina at about 495' F., 500 p.s.i.g., a space velocity of 0.47 and a hydrogen recycle rate of 3100 s.c.f./bbl. Inspection tests of the charge stock are shown in. column of Table l, the data of similar tests on the refined oil prodnet are given in column P of Table 1.

processing sequence ot the Table I 001. A 001. B Col. C Col. D Col. E 001. 1' Col. G Col. 1!

Charge 1 Hydmfln Charge 1 Hydrofln Charge 1 Hydnofln. Charge 1 Hydrofin.

Stock Stock Oil Sto Oil Stock Oil Gravity, API 27. 1 28. 7 27. 2 27. 7 27. 1 28. 0 27. 1 27. 0 Viscosity, BUS, 210.-- 110. 6 114. 124. 6 121. 0 114. 3 100 114.3 112 Visoosi Index 98. 1 08. 3 95. 2 95. 6 97. 5 98. 5 97. 5 27. 5 Color ag-Robinson 2% 4% 2 5% 2% 3% 2% 3% Pour loint, "-1 +5 10 10 a 1o 10 Sulfur, Bomb, wt. pereen 0.32 15 0. 14 0.12 0.23 0. 16 0.23 0.23 Carbon Residue. wt. pereen 0. 56 54 0. 43 0. 42 0. Neut. N0., AST'M 0.04 0.03 0.05 0.09 Operating Conditions:

Temp., F 500 607 417 465 Pressure, p.s.i.g 500 500 500 500 Catalyst Molybde- Molybde- Molybde- Molybdenum num Sulnum Sulnum Sulllde. flde. tide. tide. Space Velocity (v./v./hr.) l. 44 0. 0. 0. 56 ROOYOIBHQFOOCRSM(BALL/B1101.) 3, 140 4, 100 3, 600 3, 200

Col. I 001. J Col. K 00]. L 001. M Col. N 001. 0 Col. P

Charge H rofln. Charge Hydrofln Charge Hydrofln. Charge Hydrofln Oil 1 Oil Oil I Oil Oil Oil Oil 1 Oil Blend Blend Blend Blend Gravity, API 27.4 27. 7 27.4 27. 5 27. l 27. 7 27.2 27.3 Viscosity, SUB, 210... 134. 3 1%. 3 134. 3 126. 3 116. 5 114. 0 124. 6 123. 8 Viscosity Index 96. 5 97.,5 96. 5 97. 5 98. 1 97. 0 95. 2 95. 3 Color, Tagblnaon 2% 0 2K 4% 2% 4} 2 8} Pour Point, F 10 10 10 5 10 10 15 10 Sulfur, Bomb, wt. percen 0.25 0. 12 0.25 0.08 0.32 0.18 0. l4 0. 15 Carbon Residue, wt. pereen 0. 40 0. 33 0. 46 0. 35 0. 56 0. 52 0.43 0. 38 Neut. N0. ASTM 0.03 0.04 0.03 0.03 Operating Conditions:

Temp., F 575 575 500 495 Pressure, p I a 2,000 1,000 500 Catalyst 4 Cobalt Molybde- Molybde- Molybde- Molybnum num Sulnum Buldate. flde. fide. llde. Space Velocity (v./v.lhr.) 0.25 0. 23 1. 0. 47 Recycle H; FeedRate (s.c.i./Bbl.), 10,000 10, 000 3, 360 3, 100

1 The propane dermphalted, iurtural refined, methyl ethyl ketone-benzene dewaxed paraflln base residual lubricating oil traction.

umlnn carrier.

I The catalysts are supported on an al Comparison of the data shown in the above Table I for the charge oil with the data obtained on the product oil after hydrogen treatment indicates that when judged by standard test methods the properties of the product oil ostensibly may not appear to have been substantially altered. The apparent results of the hydrogen treating step can be briefly summarized as bringing about some slight improvement in color, some reduction in sulfur content, little or no alteration in carbon residue and little, if any, change in the viscosity index of the oil. In sub stance, the product oils have been only slightly modified CONTINENTAL ENGINE TEST The hydrogen treated oil product of Example 6 was evaluated by' means of a Continental engine test to demonstrate the beneficial effects resulting from the novel ing a Saybolt viscosity of approximately seconds at 210 F.

In order to meet this viscosity requirement, the product oil of Example 6 in an amount of 75 percent by volume was blended with 25 percent by volume of a highly refined wax distillate oilobtained from a sweet crude to form a base oil.

(inspection tests on the highly refined lubricating oil obtained from a wax distillate which was employed as the blending oil are set forth in Table II below.)

The resulting base oil, in an amount of 97.2 volume percent was then admixed with 2.8 volume percent of a lubricating oil additive comprising a mixture of magnesium alkyl phenolate and zinc alkyl phenolate, wherein the alkyl group substituents on the benzene nucleus of each phenolate contains about 23 carbon atoms. Into the resulting base oil containing the phenolate additives there was added an anti-foaming agent in an amount of parts of anti-foam agent per million parts of oil and phenolate additive. The anti-foam agent was a dimethyl silicone polymer having a kinematic viscosity of about 1000 centistokes at 25 C. The resulting mixture of base oil, phenoiate additive and silicone anti-foamant form d 7 the blended test oil. Inspection tests on the blended test oil are shown in column D of Table II.

of reducing an engine's condition after operation under controlled conditions to a numerical description. An

Table 11 001. A 001. B O CO]. D 001. I

d t Base Oil Highly re- "Sit v. o: fined lnhrl- Blended ereneo Ex. 6 Ex. 6 oil cating oil Test Oil Oil "A" (Col. L, of oil item a we: Table I) 001. distillate Gravity, APL 27. s 27.7 29.2 27.1 23.2 rnuqlfi l 12s a 91 ass 01 can "1-,: "1.2 1. ms 2 V. 5 1o 5 15 M10 cent 0.08 0. 12 0.2a ig'gn fi ffiun 0.35 an 0.02 0.45 Ba No.. 0. 10 None As pm t o. 12 0. 10 N out. N 0.06 0.03 0.09

For purposes of comparison, inspection tests on reference oil A are also shown inTable II. The reference oil A consists essentially of a blend of highly refined mineral lubricating oil consisting of 70 percent residual oil having an SUS viscosity at 210 F. of 145.9, a 27.3 API gravity and a viscosity index of 98.4; and percent of a distillate oil having an SUS viscosity at 21051. of 47.0, 31.7 API gravity and a viscosity index of 101.5.

The Continental engine test was carried out on a 4- cylinder Continental A-80 engine employing as the fuel an aviation gasoline grade AV-80 plus 3 cc. TEL per gallon and with the test oil in the crankcase of the engine. The following engine operating conditions were maintained during the test run:

Top Ring Travel Temperature Cylinder 1, 4l0 F. Cylinder 2, 390 F. Cylinder 3, 420 F. Cylinder 4, 350 F. Duration 140 hours The results of this engine test are shown in column 1 of Table III below. For purposes of comparison, the reference oil A of Table Ii above (column E) was also subjected to the Continental engine test and these test results are likewise presented in Table III, column 2.

Table III CONTINENTAL ENGINE 'rns'r The demerit rating system provides a visual means engine part which is clear or otherwise in excellent condition is assigned a numerical value of 0 demerit, whereas a rating of 10 demerits represents the worst conditions for the particular part. Total demerits is the sum of the individual demerit rating of the engine parts being in- The data in Table III show that the paraifin base residual lubricating oil fraction .processed bythe refining sequence of the present inventionpossesses a significant degree of superiority over the prior type refined reference oil in respect to a decreased amount of piston ring wear and blowby. Moreover, the data demonstrate that an aircraft engine oil obtained from a paraflin based residuum after being refined in accordance with the process of this invention exhibits unexpected beneficial efiects on the cleanliness of the pistons and somewhat less corrosion on the exhaust valve guides than the reference oil.

CF'R ENGINE TEST A series of engine tests were conducted on the deasphalted, solvent refined, dewaxed and hydrofinished oil produced by the refining sequence of the present invention to demonstrate the improved detergency characteristics and superior oxidation stability of the product oil. The reference oil I described hereinafter was also subjected to engine testing under the hereinafter set forth test conditions. The results of these engine tests are set forth in Table IV below.

The test engine consisted of a standard CFR single cylinder internal combustion engine, modified to provide an improved power section and a dry sump oil system was operated on /145 aviation gasoline under the following test conditions:

Table IV DEMERIT RATING R Test Oil Skirt Ring Rin Under Total Grooves Len Piston Demerits 1 Oil Blend of Ex. 6 (Table I, 001. L) 86 77 81 50 294 2 Ref. Oil I 86 79 83 55 303 3 Exp. Oil of Ex. 3 plus 0.5% additive agent "A" L--. 81 78 80 50 7,39 4 Ref. Oil I plus 0.5% additive agent "A" l 86 81 85 55 307 5 Exp. oil of Ex. 3 plus 0.5% additive agent 11' plus 46 59 60 45 210 2.8% additi ve agent B 1 plus 150 p.p.m. additive a n u n 6 RefkQiIJgI DIUS like amounts additive agents A," 78 70 73 45 266 'Itefer'enw oil I, a prior type highly refined mineral lubricating oil havin viscosity at 210 F. of 118 SUS and a VI of 97. The refined oil was obtained gJan API gravity of 273, an SUB y solvent deasphalting, solvent refinin solvent dewaxing, clay contacting and clay filtering a residual fraction of a paraflin based crude oil.

1 Ad itive agent A, a conventional viscosity index improver and pour point depressant consisting essential! of 40 vol. percent solution of a pol ester of methacrylic acid having a molecular weight of l0,000l5,000 in a Mi Continent solvent-refined neu oil solvent.

2 Additive agent B, a mixture of a magnesium alkyl phenolate and a zinc alkyl phenolate wherein the alkyl substituents on each benzene nucleus of each phenolate compound contains a total of about 23 carbon atoms.

! Additive agent 0, comprising a dimethyl silicone polymer anti-foam agent having a kinematic viscosity at 25 C. of about 1000 oentlstokes.

. Runs 1 and 3 of the above Table IV demonstrate that residual oils refined in accordance with the refining process of the present invention possess improved detergency characteristics and oxidation stability in comparison with oils refined by the prior type refining sequcnce. The uniform improvement in engine cleanliness is especially significant. Run 5 was made to evaluate the response of the experimental oil to blending with additive materials customarily employed in lubricating oil formulations. A comparison of the demerits assigned to the experimental oil containing the additives shows that its response to the incorporation therewith of conventional types of additive materials is considerably better than the response of the prior type refined oil. Moreover, the almost 27% decrease in total demerit rating resulting from the addition of thc additive materials (from 289 demerits for the experimental oil used in run 3, to only 210 demerits for the oil with the additives), as compared to only approximately a 13.4% decrease for the prior type refined oil containing a similar amount of the same additive is a further indication of the beneficial effects flowing from the novel refining sequence of the present invention.

PANEL COKING TEST A panel coking test was conducted to evaluate the performance of the experimental aircraft engine oil produced by the refining sequence of the present invention in respect to the stability of the oil toward thin-film oxidation at high temperatures.

The procedure for conducting the panel coking test is described in the requirements of MIL-L-7808C military specification. Briefly, the coking test of that specification comprises splashing the test fluid contained in a gravity filled reservoir onto a heated overhead aluminum panel by means of a-rotating wire brush. The panel is maintained at the test temperature (600 F.) by means of a conventional automatic temperature control unit. The aluminum panel is carefully cleaned and weighed at the start of the test and reweighed after the test run. The weight of coke deposited on the panel is thereby determined and this value is taken as a measure of the oxidation stability of the test oil.

A modified panel coking test, hereinafter referred to as "modified coking test C was employed to evaluate the stability of the experimental oil to thin-film oxidation at high temperatures. The procedure employed in the modified coking test C was as follows: The test oil in an amount of 120 grams was mechanically admixed with 0.240 gram of a commercial grade of carbon black having a particle size of 18 millimeters and an effective surface of 201 square meters/gram for minutes. The resulting blended oil in an amount of 106 grams was then added to the oil container of a modified type of a panel coking test unit apparatus model C obtained from RoxanaMachine Works, Roxana, Illinois. A polished weighed aluminum test panel was emplaced in the test unit and heated to a temperature of 620 F. with continuous mechanical stirring of the oil. When the panel temperature reached 620 F. stirring was continued for 5 additional minutes and the run was continued for an additional 40 minutes while maintaining the panel temperature at 620' F. During the aforementioned 40 minutes test period, the operation of the stirrer was controlled by a timer to permit the stirrer to operate on a repeating cycle of 2 minutes stirrer on" and 4 minutes stirrer off. After the 40 minute test period referred to above had elapsed, heating of the panel was discontinued and the panel was permitted to cool until its temperature was 300 F. The oil was continuously stirred during the cooling period. When the panel temperature reached 300, the panel was removed from the unit, and then the panel was allowed to cool further until it reached room temperature. Thereafter the cooled panel was rinsed with pentane, then rubbed briskly with a pentane-soaked cloth for 10 back-and-forth strokes, dried on a steam plate for three minutes, and cooled (to room temperature again) and weighed. The rubbing process was then repeated, and the panel was reweighed; the second weighing was recorded as the final panel weight. The difference between the original panel weight and the final panel weight was reported as the weight of coke deposits.

This modified panel coking test C is designed as a bench test for evaluating aircraft engine lubricating oils under more severe conditions than those prescribed in the panel coking test itself.

A further modification of the basic panel coking test .was also employed to evaluate the test oil under simulated conditions of severe oil starvation. The procedure used in this modification, hereinafter referred to as modified panel coking test F was the same as the procedure set forth in describing modified panel coking test C with the following essential differences, which are presented in tabular form:

Baking Dust Fl shing D ration. Total Duration..-"

The results obtained by these modified panel coking tests namely, by test methods C" and "F on a representative experimental oil refined by the method which forms the inventive subject matter of the present application are shown in Table V below. Data obtained from subjecting a prior type refined oil to similar tests 1 Reference oil 1" of Table IV above. 1 Reference oil II", a highly refined mineral lubricating oil having an API gravity of 27.3", a viscosity of 210 F. ot'146 SUB, a VI of 98.5.

The results of the above tests show that lubricating oil stocks treated in accordance with the refining sequence of the present invention possess improved stability to thin-film oxidation at high temperatures. In addition, the deasphalted, solvent refined, dewaxed and hydrogenated lubricating oil product of Example 6, Table I shows an outstanding degree of stability to thin-film oxidation in comparison with the highly refined reference oil.

Obviously, many modifications and variations of the process of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and, therefore only such limitations should be imposed as are indicated in the foregoing description.

I claim? I. A process for the treatment of a lubricating oil stock to enhance the quality thereof which consists essentially of subjecting a parafin base residual lubricating oil fraction to refining treatment including solvent deasphalting, solvent refining and solvent dewaxing and thereafter contacting the resulting treated oil with added hydrogen in the presence of a mild hydrogenation catalyst under conditions from about 400 F. to about 650 F. a pressure within the range of from about 500 to about 1000 p.s.i.g., and a space velocity of from about 0.23 to 2.0 to effect reactions converting said treated oil into a product oil having improved stability to thin-film oxidation at high temperatures.

2. A process for the treatment of a lubricating oil stock to enhance the quality thereof which consists essentially of subjecting a parafiin base residual lubricating oil fraction to treatment consisting of in sequence solvent deasphalting, solvent refining and solvent dewaxing to produce an intermediate product having about 27 API gravity, a Saybolt Universal seconds viscosity at 210 F. of about 114 to 134, and a viscosity index of about 95 to about 98, and thereafter subjecting said intermediate product in admixture with added hydrogen and in the presence of a mild hydrogenation catalyst to a temperature of about 400 F. to about 650 F. a pressure of about 500 to 1000 p.s.i.g., and a space velocity of about 0.25 to about 1.0 for a period of time such that said intermediate product is converted to a lubricating oil having improved stability to thin-film oxidation at high temperatures.

3. A process for the treatment of a lubricating oil stock to enhance the quality thereof which consists essentially of subjecting a paraflin base residual lubricating oil fraction to refining treatment consisting of in sequence propane deasphalting, furfural refining and methyl ethyl ketone-benzene solvent dewaxing, and thereafter contacting the resulting treated oil with added hydrogen in the presence of a mild hydrogenation catalyst under conditions of about 400 F. to 650 F., about 50010 about 1000 p.s.i.g. and a space velocity of from about 0.25 to about 1.0 to efiect reactions converting said treated oil into a product oil having increased stability to thin-film oxidation at high temperatures.

4. The process as claimed in claim 3 wherein said catalyst comprises 20 percent molybdenum sulfide on alumina.

5. The process as claimed in claim 3 wherein the deasphalted, solvent refined, and dewaxed oil is contacted with added hydrogen at a temperature within the range of from about 500 F. to 600 F. in the presence of a molybdenum sulfide hydrogenation catalyst.

6. A method of processing a lubricating oil stock which consists essentially of subjecting a propane deasphalted, furfural refined, methyl ethyl ketone-benzene solvent dewaxed paraflin base residual lubricating oil fraction to the influence of added hydrogen and mild hydrogenation conditions including temperatures ranging from about 500 F. to 600 F. and pressures ranging from about 500 p.s.i.g. to about 1000 p.s.i.g. and a space velocity of from 0.23 to 1.0 in the presence of a molybdenum sulfide catalyst for a period suificient to produce a lubricating oil having improved stability to thin-film oxidation at high temperatures, and thereafter recovering said improved lubricating oil.

7. The method as claimed in claim 6 wherein a base stock feed rate of about 0.25 to 0.50 volume of feed per volume of catalyst per hour is employed.

8. The method as claimed in claim 6 wherein hydrogenation conditions are a temperature of about 575 F., a pressure of about 1000 p.s.i.g. and a base stock feed rate of about 0.23 volume per volume of catalyst feed per hour.

9. The method as claimed in claim 6 wherein the hydrogen consumption is in the range of from 50 to 350 standard cubic feet per barrel of feed.

10. An aircraft engine lubricating oil having improved stability to thin film oxidation at high temperatures, said oil having an API gravity within the range of from about 27 to about 29, a viscosity index within the range of from about to about 98.5, a viscosity within the range of from about 109 to about 126 Saybolt Universal seconds at 210, a color (Tag Robinson scale) within the range of from about 3.5 to about 6, a pour point within the range of from about 5 F. to about 10 F., a carbon residue within the range of from about 0.33 to about 0.54% by weight, a sulfur (bomb) content within the range of from about 0.08% to about 0.23% by weight, and a neutralization number within the range of from about 0.03 to about 0.09, said oil being the product obtained by in sequence subjecting a paraflin base residual lubricating oil fraction to solvent deasphalting, solvent refining, and solvent dewaxing and thereafter hydrogenating the resulting treated oil fraction with added hydrogen and in the presence of a hydrogenation catalyst selected from the group consisting of molybdenum sulfide and cobalt oxide-molybdenum oxide at a temperature within the range of from about 417 to about 606 F., a pressure within the range of from about 500 to about 1000 p.s.i.g., a space velocity within the range of from about 0.23 to about 1.7 and a hydrogen recycle rate of fiom about 3100 to'about 10,000 standard cubic feet of hydrogen per barrel of oil.

References Cited in the file of this patent UNITED STATES PATENTS glufity, The Oil and Gas Journal, Nov. 1, 1954, pages 

1. A PROCESS FOR THE TREATMENT OF A LUBRICATING OIL STOCK TO ENHANCE THE QUALITY THEREOF WHICH CONSISTS ESSENTIALLY OF SUBJECTING A PARAFFIN BASE RESIDUAL LUBRICATING OIL FRACTION TO REFINING TREATMENT INCLUDING SOLVENT DEASPHALTING, SOLVENT REFINING AND SOLVENT DEWAXING AND THEREAFTER CONTACTING THE RESULTING TREATED OIL WITH ADDED HYDROGEN IN THE PRESENCE OF A MILD HYDROGENATION CATALYST UNDER CONDITIONS FROM ABOUT 400*F. TO ABOUT 650* F. A PRESSURE WITHIN THE RANGE OF FROM ABOUT 500 TO ABOUT 1000 P.S.I.G., AND A SPACE VELOCITY OF FROM ABOUT 0.23 TO 2.0 TO EFFECT REACTIONS CONVERTING SAID TREATED OIL INTO A PRODUCT OIL HAVING IMPROVED STABILITY TO THIN-FILM OXIDATION AT HIGH TEMPERATURES.
 10. AN AIRCRAFT ENGINE LUBRICATING OIL HAVING IMPROVED STABILITY TO THIN FILM OXIDATION AT HIGH TEMPERATURES, SAID OIL HAVING AN API GRAVITY WITHIN THE RANGE OF FROM ABOUT 27*F TO ABOUT 29*, A VISCOSITY INDEX WITHIN THE RANGE OF FROM ABOUT 95 TO ABOUT 98.5, A VISCOSITY WITHIN THE RANGE OF FROM ABOUT 109 TO ABOUT 26 SAYBOLT UNIVERSAL SECONDS AT 210*, A COLOR (TAG ROBINSON SCALE) WITHIN THE RANGE OF FROM ABOUT 3.5 TO ABOUT 6, A POUR POINT WITHIN THE RANGE OF FROM ABOUT 5*F. TO ABOUT 10*F., A CARBON RESIDUE WITHIN THE RANGE OF FROM ABOUT 0.33 TO ABOUT 0.54% BY WEIGHT, A SULFUR (BOMB) CONTENT WITHIN THE RANGE OF FROM ABOUT 0.0,% TO ABOUT 0.23% BY WEIGHT, AND A NEUTRALIZATION NUMBER WITHIN THE RANGE OF FROM ABOUT 0.03 TO ABOUT 0.09, SAID OIL BEING THE PRODUCT OBTAINED BY IN SEQUENCE SUBJECTING A PARAFFIN BASE RESIDUAL LUBRICATING OIL FRACTION TO SOLVENT DEASPHALTING, SOLVENT REFINING, AND SOLVENT DEWAXING AND THEREAFTER HYDROGENATING THE RESULTING TREATED OIL FRACTION WITH ADDED HYDROGEN AND IN THE PRESENCE OF A HYDROGENATION CATALYST SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM SULFIDE AND COBALT OXIDE-MOLYBDENUM OXIDE AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 417* TO ABOUT 606*F., A PRESSURE WITHIN THE RANGE OF FROM ABOUT 500 TO ABOUT 1000 P.S.I.G., A SPACE VELOCITY WITHIN THE RANGE OF FROM ABOUT 0.23 TO ABOUT 1.7 AND A HYDROGEN RECYCLE RATE OF FROM ABOUT 3100 TO ABOUT 10,000 STANDARD CUBIC FEET OF HYDROGEN PER BARREL OF OIL. 